We often get asked about the multiple use voltage converters which both stepdown to 110v and step-up up to 220v.
We not only don’t sell them, we don’t recommend them to our customers for some very important reasons:

Primarily they can damage your equipment due to under voltage.
Our engineer explains why this is so:
The technical Explanation of Step Down/Step Up Transformer Operation:


  1. On No load voltage = 120v
  2. On Full load voltage = 110v

So, if you try to reverse the transformer you feed 110v into a 120v winding to give not 240v you get 110 x 240/120 = 220v rms.

Hence, the voltage to the appliance is low. Now, if the applied voltage (input voltage) drops to 110-6% (as is allowed by the power utility supplier), the voltage will be 105.4 x 240/120 = 210.80v. This is VERY LOW!

Hence, the voltage will be so low on the 240v appliance. A motor with this voltage may stall due to the low voltage. The motor output power will be reduced to (210.8/240) x 100 = 77% output only.


This is not satisfactory. You need a dedicated step up transformer for such an application and a dedicated step down transformer for that individual application. You cannot successfully use a step down transformer in the reverse voltage operation method, to step up the voltage. It is incorrect and will cause under voltage problems on the customers equipment.